When material is being moved on a transporting system, it is often necessary to ensure that the material does not overhang or project beyond a front edge, and also a rear edge, of a transporting structure. An overhang can cause serious problems in an automatic storing system. If, for example, there is an overhang on a pallet and it is being transported to a position in a store, the pallet with the load may not fit into the storing location because of the overhang. The overhang may also cause a collision with structures of the storing system to take place. Such situations are to be avoided, since they effect productivity and cause damage to the load, or possibly the storing or transporting system.
In a known embodiment, for example, a pallet is stopped in a predefined position or a sensor with which the pallet can be detected, in order for its movement then to be stopped, is used. A light curtain with light barriers is provided a little away from the front edge of the pallet. When the output of the light curtain indicates an interruption of the light barriers, an overhang of material is protruding beyond the front edge of the pallet. The output of the light curtain can then be used to remove the pallet from the storing operation or to output a warning about the problem to the operating personnel.
A corresponding procedure can be used, not only for the front edge of the pallet, but for its rear edge also. If the pallet is arranged in such a way that the light curtain is positioned just behind the rear edge of the pallet, it can be established with the light curtain whether something is overhanging beyond the rear edge of the pallet.
In the case of one embodiment, the storing operation is only continued when both tests have been completed and the light curtain has not been interrupted in either test.
The test for the presence of an overhang accordingly requires a certain amount of time, by which the storing operation is prolonged.